Metal-Free Activation of the Donor-Acceptor Cyclopropanes: Protic Acids, Bases, and Thermal Reactions

In the past decades, remarkable progress has been made in the field of metal-free activation of donor-acceptor (D-A) cyclopropanes. This chapter focuses on introducing various strategies for the C-C bond cleavage of the D-A cyclopropanes by means of protic acids, non-metal Lewis acids, bases, thermal reactions, and so on. Four main sections based on different modes of activation, including electrophilic activation, nucleophilic activation, catalyst-free activation, and activation of D-A cyclopropanes via radical process, are reviewed and discussed.